U.S. patent application number 13/829985 was filed with the patent office on 2014-09-18 for low friction camshaft with electric phaser.
The applicant listed for this patent is Mahle Engine Components USA, Inc.. Invention is credited to Daniel M. Lonowski.
Application Number | 20140261265 13/829985 |
Document ID | / |
Family ID | 51520015 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140261265 |
Kind Code |
A1 |
Lonowski; Daniel M. |
September 18, 2014 |
LOW FRICTION CAMSHAFT WITH ELECTRIC PHASER
Abstract
An exemplary engine assembly includes a crankshaft, and a
camshaft having cam lobes mounted thereon. The cam lobes are
configured to provide lift to respective devices as a function of a
rotation of the camshaft. The cam lobes are circumferentially
offset from one another such that a timing of operation of the lift
is different for each of the at least two cam lobes. The assembly
includes at least one roller bearing coupled to the camshaft, and
an electric cam phaser configured to alter the timing of the
camshaft with respect to the crankshaft as a function of engine
operation.
Inventors: |
Lonowski; Daniel M.; (Novi,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mahle Engine Components USA, Inc. |
Muskegon |
MI |
US |
|
|
Family ID: |
51520015 |
Appl. No.: |
13/829985 |
Filed: |
March 14, 2013 |
Current U.S.
Class: |
123/90.17 ;
29/888.01 |
Current CPC
Class: |
F16C 2360/18 20130101;
F01L 2001/0476 20130101; F01L 1/344 20130101; F01L 2001/0473
20130101; F01L 1/34413 20130101; F16C 19/466 20130101; F16C 21/00
20130101; Y10T 29/49231 20150115 |
Class at
Publication: |
123/90.17 ;
29/888.01 |
International
Class: |
F01L 1/344 20060101
F01L001/344 |
Claims
1. An engine assembly comprising: a crankshaft; a camshaft having
at least two cam lobes mounted thereon, the at least two cam lobes
configured to provide lift to respective devices as a function of a
rotation of the camshaft, wherein the at least two cam lobes are
circumferentially offset from one another such that a timing of
operation of the lift is different for each of the at least two cam
lobes; at least one roller bearing coupled to the camshaft; and an
electric cam phaser configured to alter the timing of the camshaft
with respect to the crankshaft as a function of engine
operation.
2. The engine assembly of claim 1, wherein the at least one roller
bearing is one of a conical roller bearing, a ball bearing, a
needle bearing, and a cylindrical bearing.
3. The engine assembly of claim 1, wherein at least one of the
roller bearings coupled to the camshaft operates without a
lubricating oil feed.
4. The engine assembly of claim 3, wherein all of the roller
bearings coupled to the camshaft do not have a lubricating oil
feed.
5. The engine assembly of claim 1, wherein: the camshaft is
comprised of an inner shaft and an outer shaft that is outside the
inner shaft; one of the at least two cam lobes is mounted to the
inner shaft; another of the at least two cam lobes is mounted to
the outer shaft; and the electric cam phaser is a cam phaser
assembly that provides dual independent control and is configured
to rotate the inner shaft with respect to the outer shaft.
6. The engine assembly of claim 1, wherein the respective devices
are one of a valve, an injection pump, a vacuum pump, a fuel pump,
or other actuated device.
7. The engine assembly of claim 1, wherein the engine assembly is
one of a spark ignition (SI) engine and a compression ignition (CI)
engine.
8. A method of manufacturing an engine, comprising: providing a
crankshaft; providing a camshaft having multiple lobes configured
to provide mechanical action to respective devices as a function of
a rotation of the camshaft, wherein the at least two cam lobes are
circumferentially offset from one another such that a timing of
operation of the mechanical action is different for at least two of
the multiple cam lobes; coupling at least one roller bearing to the
camshaft; coupling an electric cam phaser between the camshaft and
the crankshaft; and configuring the electric cam phaser to alter
the timing of the camshaft with respect to the crankshaft as a
function of engine operation.
9. The method of claim 8, wherein coupling at least one roller
bearing to the camshaft comprises coupling one of a conical roller
bearing, a ball bearing, a needle bearing, and a cylindrical
bearing.
10. The method of claim 8, wherein coupling the at least one roller
bearing to the camshaft comprises coupling at least one of the
roller bearings to the camshaft that does not have a lubricating
feed.
11. The method of claim 8, wherein coupling the at least one roller
bearing to the camshaft comprises coupling roller bearings to the
camshaft that are all without a lubricating feed.
12. The method of claim 8, wherein: providing the camshaft
comprises providing an inner shaft concentrically placed within an
outer shaft such that both inner and outer shafts rotate with
respect to a central rotation axis; and further comprising:
mounting one of the at least two cam lobes to the inner shaft;
mounting one of the at least two cam lobes to the outer shaft; and
wherein configuring the electric cam phaser further comprises
configuring the electric cam phaser assembly to provide dual acting
control and to rotate the inner shaft with respect to the outer
shaft.
13. The method of claim 8, wherein providing the camshaft to
provide the mechanical action further comprises providing the
camshaft to provide the mechanical action to the respective devices
that are one of a valve, an injection pump, a vacuum pump, and a
fuel pump or other actuated device.
14. The method of claim 8, wherein the engine is one of a spark
ignition (SI) engine and a compression ignition (CI) engine.
15. A camshaft assembly comprising: a camshaft having at least two
cam profiles positioned along respective axial locations, the at
least two cam profiles configured to provide lift to respective
devices of an engine, wherein the at least two cam profiles are
circumferentially offset from one another such that a timing of
operation of the lift is different for each of the at least two cam
profiles; and at least one roller bearing coupled to the camshaft;
an electric cam phaser coupled to the camshaft and coupleable to a
crankshaft, the electric cam phaser configured to alter the timing
of the camshaft with respect to the crankshaft as a function of
engine operation.
16. The camshaft assembly of claim 15, wherein the at least one
roller bearing is one of a conical roller bearing, a ball bearing,
a needle bearing, and a cylindrical bearing.
17. The camshaft assembly of claim 15, wherein at least one of the
roller bearings coupled to the camshaft does not have a lubricating
oil feed.
18. The camshaft assembly of claim 17, wherein all of the roller
bearings coupled to the camshaft do not have a lubricating oil
feed.
19. The camshaft assembly of claim 15, wherein: the camshaft is
comprised of an inner shaft and an outer shaft that is outside the
inner shaft; one of the at least two cam profiles is mounted to the
inner shaft; another of the at least two cam profiles is mounted to
the outer shaft; and the electric cam phaser is an electric cam
phaser assembly that provides dual independent control and is
configured to rotate the inner shaft with respect to the outer
shaft.
20. The camshaft assembly of claim 15, wherein the respective
devices are one of a valve, an injection pump, a vacuum pump, and a
fuel pump or other actuated device.
Description
BACKGROUND
[0001] Engine manufacturers are constantly seeking to increase
power output and fuel efficiency of their products. One method of
generally increasing efficiency and power is to reduce the friction
within a camshaft of the engine.
[0002] Camshafts are typically used to control valve motion and
other important timing events in internal combustion engines. The
camshaft is a shaft having axially spaced cams or cam lobes, which
project outwardly from the surface of the shaft. The shaft and cams
can be machined from a single part and may also be assembled from
separate parts. The camshaft is typically supported by bearings,
such as journal bearings that are positioned between the cams along
the axial direction of the camshaft. The journal bearings (or fluid
film or sleeve bearings) operate by means of a fluid film of oil,
typically fed to the bearings via a pressurized feed through
drillings in the bearing housing or other routes.
[0003] The engine includes a crankshaft that can be directly
coupled to the camshaft using gears, belts, chains, and the like.
Thus, the crankshaft is a reference shaft from which timing events
are determined for other engine operations. The camshaft may be
independently controlled relative to the crankshaft to improve
engine efficiency. One known device for independently controlling
the camshaft relative to the crankshaft is a cam phaser. A cam
phaser on a camshaft provides variable camshaft rotation to improve
engine timing and lift events, leading to improved engine
efficiency. Overall efficiency is improved at least in part because
it may be desirable to alter the relative timing between the
camshaft and the crankshaft, depending on the condition of
operation of the engine. For instance, at idle the relative timing
between the two shafts may have one desired timing, which may
differ when the engine is a high speed operation.
[0004] Various cam phasing technologies are used to accomplish
variable cam phasing, including helical spline phasers, hydraulic
vane rotor phasers, and cam torque actuated phasers. Variable cam
phasing or timing accommodates the divergent needs for power and
torque output, idle stability, fuel economy, and emissions control,
as examples. These cam phasing technologies require a pressurized
oil feed from the engine hydraulic pump for their operation.
Because the engine includes hydraulic feed for the bearings, oil
from the hydraulic system is typically thereby fed to the cam
phaser as well.
[0005] The demands on the hydraulic pump for supplying oil to
bearings divert power output away from other engine operations.
These parasitic power losses reduce the engine's efficiency. The
parasitic losses are increased with the presence of a cam phaser
because of its oil feed. Thus, despite improved engine efficiency
with the use of variable camshaft/crankshaft timing, parasitic
losses from the cam phaser and the bearings prevent the engine from
operating at its peak efficiency.
[0006] Accordingly, there is a need for an improved camshaft for an
internal combustion engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Referring now to the drawings, illustrative examples are
shown in detail. Although the drawings represent the exemplary
illustrations described herein, the drawings are not necessarily to
scale and certain features may be exaggerated to better illustrate
and explain an innovative aspect of an exemplary illustration.
Further, the exemplary illustrations described herein are not
intended to be exhaustive or otherwise limiting or restricting to
the precise form and configuration shown in the drawings and
disclosed in the following detailed description. Exemplary
illustrations are described in detail by referring to the drawings
as follows:
[0008] FIG. 1 is an exemplary engine assembly;
[0009] FIGS. 2A and 2B illustrate exemplary cam lobe profiles that
can be incorporated into the engine assembly of FIG. 1; and
[0010] FIGS. 3A-3D illustrate exemplary bearing arrangements that
can be incorporated into the engine assembly of FIG. 1.
DETAILED DESCRIPTION
[0011] Reference in the specification to "an exemplary
illustration", an "example" or similar language means that a
particular feature, structure, or characteristic described in
connection with the exemplary approach is included in at least one
illustration. The appearances of the phrase "in an illustration" or
similar type language in various places in the specification are
not necessarily all referring to the same illustration or
example.
[0012] In some exemplary illustrations, components of an engine are
shown that includes a camshaft that is coupled to a crankshaft. The
camshaft includes at least two cam lobes mounted thereon, and the
two cam lobes are configured to provide lift to respective devices
as a function of a rotation of the camshaft. The cam lobes may be
circumferentially offset from one another such that a timing of
operation of the lift is different for the cam lobes. The camshaft
includes at least one roller bearing coupled to the camshaft. An
electric cam phaser is configured to alter the timing of the
camshaft with respect to the crankshaft as a function of engine
operation.
[0013] Turning now to FIG. 1, an exemplary engine assembly 100 is
shown. Engine assembly 100 is an internal combustion (IC) engine
according to one embodiment and a compression ignition (CI) engine
according to another embodiment. Engine assembly 100 provides
motive power to a vehicle such as a car, truck, bus, etc. However,
the applications are not limited to those listed and may be
applicable to any device that may derive motive power from an
engine assembly such as engine assembly 100.
[0014] Engine assembly 100 includes a timing input or crankshaft
102 and a camshaft 104 that are coupled to one another via an
electric cam phaser 106. Crankshaft 102 is configured to rotate in
a crankshaft rotation direction 108 and about a crankshaft rotation
axis 110. Crankshaft 102 includes a number of elements, not shown,
that include but are not limited to crank throws or crank pins that
are radially offset from crankshaft rotation axis 110. During
rotation, the crankshaft throws provide a reciprocating motion to,
as one example, pistons within cylinders. The angular orientation
of the crankshaft throws, with respect to one another, controls
motion of the pistons with respect to one another. The relative
rotation is of the crankshaft throws is coupled to timing of the
combustion events within the cylinders. According to one example,
element 102 is simply a timing reference device from which timing
events in the are determined.
[0015] Camshaft 104 includes, in the illustrated example, two cam
lobes 112, and camshaft 104 is configured to rotate about a
rotational axis 114, independent of rotation 108 of crankshaft 102.
Rotational axis 114 is shown to be collinear with rotational axis
110; however, in other exemplary approaches the two axes 110, 114
are offset from one another. Cam lobes 112 provide mechanical
action to devices within engine assembly 100, including but not
limited to a valve, an injection pump, a vacuum pump, and a fuel
pump, as examples. That is, cam lobes 112 are eccentrically shaped
or oblong devices that are positioned having a profile that
determines a timing and extent of operation that derives therefrom
and is controllable via the profile.
[0016] FIGS. 2A and 2B illustrate exemplary profiles of cam lobes.
FIG. 2A shows a cam assembly 200 having a generally circular cam
lobe 202 that is eccentrically mounted on a rotatable shaft 204.
Rotatable shaft 204 corresponds to rotational axis 114 of engine
assembly 100. Circular cam lobe 202 is offset an eccentric distance
206 from a center 208 of circular cam lobe 202. As such, when
circular cam lobe 202 is caused to rotate 210 about rotatable shaft
204 a cam follower 212 is caused to move axially 214, which causes
the mechanical action to the devices as described above.
[0017] FIG. 2B shows another example of a cam assembly 250 having
an oblong lobe or profile 252 that is mounted to rotatable shaft
204. As such, when oblong lobe 252 is caused to rotate 210 about
rotatable shaft 204, a cam follower 254 is caused to move axially
256, which again causes the mechanical action to the devices as
described above, however commensurate with the profile of oblong
lobe 252.
[0018] As such, referring back to FIG. 1, cam lobes 112 are
configured to provide lift to respective devices as a function of
rotation of camshaft 104, and cam lobes 112 are circumferentially
offset from one another such that a timing of operation of the lift
is different for each of the at least two cam lobes. Engine
assembly 100 includes bearings 116 that support camshaft 104. And,
although two cams 112 and two bearings 116 are illustrated, it is
contemplated that more cams and bearings may be included along
camshaft 104.
[0019] One or more of bearings 116 coupled to camshaft 104 are
roller bearings and may be, according to illustrative embodiments,
a conical roller bearing, a ball bearing, a needle bearing, and a
cylindrical bearing. In one embodiment, all of bearings 116 on
camshaft 102 are roller bearings. The bearings selected typically
provide an ability to carry a radial load, but one or more bearings
may also be included to also limit axial motion of the shaft.
Roller bearings, as is commonly known, may be lightly lubricated
with a residual amount of lubricant, but do not have pressurized or
replenished oil supply, and there is not pumped oil for lubrication
to operate. That is, the roller bearings do not have a lubricating
oil feed. Contrary to bearings that are typically used for a
camshaft, one or all of bearings 116 are roller bearings that
operate in an operation that does not include a pressurized oil
supply. Further, as illustrated and as discussed, electric cam
phaser 106 couples crankshaft 102 with camshaft 104.
[0020] Electric cam phaser 106 is configured to alter the timing of
the camshaft with respect to the crankshaft as a function of engine
operation. That is, electric cam phaser 106 may be an electric or
electronic device that uses brushless DC electric motors to actuate
a gear mechanism to effect cam phasing with low power consumption.
As such, cam phaser 106 does not include an oil feed and thus
operates in an oil free mode.
[0021] Various bearing and cam phaser arrangements may be
incorporated into the camshaft and in conjunction with an electric
cam phaser. FIGS. 3A-3D illustrate bearing/electric cam phaser
arrangements that can be incorporated into engine assembly 100
illustrated in FIG. 1.
[0022] Referring to FIG. 3A, bearing/cam phaser assembly 300
includes an electric cam phaser 302 that is coupled to a camshaft
304, and coupleable to a crankshaft, such as crankshaft 102 of
engine assembly 100. Assembly 300 includes cam lobes 306 and roller
bearings 308, 310, 312, and 314 that operate without an oil feed
for lubrication. In the illustrated example, roller bearing 308 is
a ball bearing that includes inner and outer races and balls that
transmit load on camshaft 304 to a support structure (not shown)
via support frame 316. Roller bearings 310-314 are needle bearings
that include a relatively large contact surface compared to ball
bearing 308. Needle bearings 310-314 also tend to have a lower
profile relative to ball bearing 308 so are more compact. Needle
bearings 310-314 include a needle cage and needle rollers that
contact and support camshaft 304 and carry the load of camshaft 304
to the support structure via support frames 318. Cam phaser 302 may
be positioned at a first end 320 of camshaft 304, or may
alternatively be positioned at a second end 322 and coupled to the
crankshaft. Thus, because cam phaser 302 is electric and because
all the bearings are roller bearings, there is no need to feed oil
to the region of the cam shaft. This reduces parasitic losses,
thereby providing an overall simpler and more compact engine design
as compared to approaches previously utilized at least in part
because the engine oil pump can be smaller, and because there are
no oil feed lines to the area of the cam shaft.
[0023] FIG. 3B illustrates another exemplary bearing/cam phaser
assembly 340 that includes cam phaser 302 coupled to camshaft 304,
cam lobes 306, ball bearing 308, and needle bearing 310. However,
in this example two journal bearings 342 are included that do not
include roller elements such as in roller bearings 308, 310.
Journal bearings 342 include contact surfaces 344 that slide over
camshaft 304. Because of the increased surface area compared to
roller bearings 308, 310, there is an increased propensity for
frictional heating as well during rotation of camshaft 304.
Accordingly, journal bearings 342 include oil feed lines 346 that
pass through their respective support frames 348. Thus, although in
this embodiment oil feed lines 346 are included to some of the
bearings (342), the parasitic losses are nevertheless reduced when
compared to a design in which all bearings are journal bearings.
Thus, with the combination of the electric cam phaser and some
roller bearings, parasitic losses to the engine are reduced and
overall engine design is simplified because of a reduced need to
provide oil feed to all of the bearings and to the cam phaser.
[0024] FIG. 3C illustrates another exemplary bearing/cam phaser
assembly 360. A cam phaser assembly 362 provides dual independent
control to two shafts of a camshaft via a first cam phaser 364 and
a second cam phaser 366. First cam phaser 364 is coupled to an
inner shaft or inner camshaft 368. Second cam phaser 366 is coupled
to first cam phaser 364 as well as to an outer shaft or outer
camshaft 370 that is radially or concentrically positioned outside
inner shaft 368. Either first cam phaser 364 or second cam phaser
366 is also coupleable to a crankshaft (not shown).
[0025] Assembly 360 includes cam lobes that are coupled to either
inner shaft 368 or outer shaft 370. In this example, a cam lobe 372
is mounted or coupled to inner shaft 368 via a pin 374, and cam
lobes 376 are mounted or coupled directly to outer shaft 370. Outer
shaft 370 is supported, in this exemplary approach, by a mix of
roller bearings and journal bearings, and inner shaft 368 is
supported by first cam phaser 364 on a first end 378 and a bearing
(not shown) on a second end 380. Inner shaft 368 and outer shaft
370 are therefore rotatable relative to one another by
independently controlling each cam phaser 364, 366, relative to
each other. Cam lobe 372 can thereby be rotationally controlled
relative to cam lobes 376. Thus, having separate cam phasers
enables an additional dimension of control to the operation of
assembly 360.
[0026] That is, both cam phasers 364, 366 may be coupled to one
another and coupled to the crankshaft, which directly couples both
shafts 368, 370 (and their respective cam lobes 372, 376) together
and to the crankshaft. However, cam phasers 364, 366 may be rotated
relative to one another such that a cam profile of cam lobe 372 can
be altered circumferentially with respect to cam lobes 376. In such
fashion, timing of lift events within assembly 360 may be further
controlled by altering rotation of both shafts 368, 370 relative to
the crankshaft, and by altering rotation of both shafts 368, 370
relative to each other.
[0027] As stated, referring still to FIG. 3C, outer shaft 370 is
supported by a mix of roller bearings and journal bearings. Thus,
in the example shown ball bearing 382 and needle bearing 384 are
included, while oil-fed bearings 386 are shown having oil feed
lines 388.
[0028] Similarly, FIG. 3D shows an exemplary assembly 394 having
cam phaser assembly 362 that enables relative motion between shafts
368, 370 and with respect to the crankshaft. However, in this
example all bearings operate without an oil feed for lubrication.
As shown in FIG. 3C, roller bearing 382 and needle bearing 384 are
shown, but assembly 394 of FIG. 3D includes needle bearings 396 as
well. Thus, because cam phaser assembly 362 is electric and because
all the bearings are roller bearings, there is no need to feed oil
to the region of the cam shaft. This reduces parasitic losses and
providing an overall simpler and more compact engine design because
the engine oil pump can be smaller, and because there are no oil
feed lines to the area of the cam shaft.
[0029] Thus, in the examples illustrated, cam shaft operation may
be controlled with respect to the crankshaft operation, and lobes
within the camshaft may be controlled with respect to one another
via an electric phaser assembly having one phaser coupled to one
shaft, and another phaser coupled to another shaft (cam-in-cam).
Further, both operations are possible and in the concentric
camshaft arrangement shafts may be controlled with respect to one
another and operation of both is controlled with respect to the
crankshaft. As such, the amount of oil fed to the engine is reduced
and there is no need for oil or hydraulic fluid for a phaser. In
addition, aside from the reduced parasitic losses, there is no need
for a rotating coupler for putting oil into the camshaft (such as,
for a slide or journal bearing). As a result, fewer engine
components are required along with the lack of need for phaser
activation. Moreover, the engine oil pump may be reduced in
size.
[0030] With regard to the processes, systems, methods, heuristics,
etc. described herein, it should be understood that, although the
steps of such processes, etc. have been described as occurring
according to a certain ordered sequence, such processes could be
practiced with the described steps performed in an order other than
the order described herein. It further should be understood that
certain steps could be performed simultaneously, that other steps
could be added, or that certain steps described herein could be
omitted. In other words, the descriptions of processes herein are
provided for the purpose of illustrating certain embodiments, and
should in no way be construed so as to limit the claimed
invention.
[0031] Accordingly, it is to be understood that the above
description is intended to be illustrative and not restrictive.
Many embodiments and applications other than the examples provided
would be upon reading the above description. The scope of the
invention should be determined, not with reference to the above
description, but should instead be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled. It is anticipated and intended that
future developments will occur in the arts discussed herein, and
that the disclosed systems and methods will be incorporated into
such future embodiments. In sum, it should be understood that the
invention is capable of modification and variation and is limited
only by the following claims.
[0032] All terms used in the claims are intended to be given their
broadest reasonable constructions and their ordinary meanings as
understood by those skilled in the art unless an explicit
indication to the contrary in made herein. In particular, use of
the singular articles such as "a," "the," "said," etc. should be
read to recite one or more of the indicated elements unless a claim
recites an explicit limitation to the contrary.
* * * * *